Conventional room temperature forming operations experience difficulties in forming very thin sheet materials without wrinkles or tears, particularly in flange areas. Where desirable results without wrinkling or tearing have been obtained with conventional methods, high speed forming of thin sheet materials is limited to thicker materials for economical production levels. For example, using conventional room temperature forming methods, aluminum sheet material less than 0.0127 centimeters (cm) (0.005 inches [in]) thick is difficult to form without wrinkles or tears. As well, high speed forming of stainless steel by conventional means has been limited to sheets 0.0254 cm (0.010 in) thick or greater.
One of the problems associated with the forming of very thin gauge materials is the lack of adequate control over workpiece slip or draw while at the same time preventing the formation of wrinkles within the flange. The tendency of the thin workpiece material is to draw into the forming tool which causes the foil to be compressed laterally in the flange region. Insufficient clamp pressure or imperfect flatness between the two mating halves of the tool results in a buckling mode type of failure of the foil which produces wrinkles. However, excessive clamping force required to prevent excessive foil movement does not solve the problem of wrinkling, as some material draw is desirable. Excessive clamping force also promotes tearing of the foil during forming. For many forming applications, for example, vacuum insulation panels, wrinkle-free flanges are required for welding vacuum tight seams. Thus, generally, wrinkling is undesirable. Tearing is unacceptable.
Accordingly, the need exists for improved apparatuses and methods for forming very thin sheet materials without buckling, wrinkling or tearing of the flange area.